Identification documents essentially comprise a card or sheet material containing information relating to the bearer. Generally, a portion of the information is in the form of a photograph. Identification cards (I.D. cards) are used e.g. to establish a person's authorization to conduct certain activities (driver's license) or the authorization to have access to certain areas (employee I.D. cards) or to engage in credit transactions (I.D. credit cards).
In view of the widespread use of I.D. cards, especially in commercial transactions, such as cashing checks, credit purchases, etc., it is important that the information contained in the I.D. card cannot be altered and that the I.D. card gives maximum protection against counterfeiting by alteration and/or replacement of its data and photograph.
Normally the information in the I.D. card is protected by lamination between plastic sheets serving as support and covering sheet.
Many attempts have been made to obtain a seal that is sufficiently strong that it resists separation, e.g. by razor blade and/or wet treatment. The use of a pouch structure wherein only the border parts of the plastic sheets are sealed is not sufficiently tamperproof since after cutting around the edge of the original card the pouch can be opened and some information such as the photograph can be removed and replaced by other information before resealing the pouch.
Ideally, to avoid said shortcoming a "security seal" is established between the information-bearing element of the card or document and the plastic. As described in U.S. Pat. No. 4,151,666 the security seal insures that if one should succeed in the removal of the plastic cover sheet, a substantial portion of the information containing part of the document is also be removed so that a damaged part remains adhering to the support. In this way protection against surreptitious substitution of information is obtained discouraging alteration of sealed documents.
Since in most cases a photograph is used that is formed in one or more hydrophilic colloid layers as are known from silver halide photography, a good bonding of said layer(s) to the plastic support sheet and plastic covering sheet is essential so that any attempted opening of the seal results in obvious damage of the photograph and other information.
According to the U.S. Pat. No. 4,456,667 a tamperproof document consists of a photographic material as information carrier which is laminated on one or both sides with a transparent resin foil. In the lamination between the hydrophilic surface of a developed gelatin-silver halide emulsion layer and said transparent foil a layer of adhesive containing a poly-1,2-alkyleneimine is applied.
It has been established experimentally by us that poly-1,2-ehtyleneimine offers poor adhesion when used in the lamination of hydrophobic resin foils such as polyethylene foils to hydrophilic colloid layers containing a cationic mordant.